Accurately and precisely determining a location of an emitter is useful in various technologies. For example, certain game systems include remote control units. A common type of remote control unit includes: a body which is gripped by a user, buttons, joysticks and/or other user-operable interface elements on the body; and hardware and software which generate and transmit commands corresponding to a user's manipulation of the interface elements to a console of the gaming system. Certain remote control units allow the user to transmit commands to the console by both manually manipulating the interface elements on the remote control unit and moving the remote control unit. Thus, accurately and precisely determining a location of an emitter on the remote control unit can allow a user of the associated gaming system to input commands to the console by moving the remote control unit.
Various obstacles and difficulties can make accurately and precisely determining the location of the emitter difficult. For example, certain methods for determining the location of the emitter rely upon time-of-flight of a pulse from the emitter to a receiver in order to determine the location of the emitter. Typical time-of-flight measurements begin timing from when a first pulse is produced. In systems with a piezoelectric ultrasonic transmitter, the piezoelectric ultrasonic transmitter does not instantly emit an ultrasonic wave upon receiving a command signal and initial waves emitted by the piezoelectric ultrasonic transmitter are generally weaker than later waves emitted by the piezoelectric ultrasonic transmitter due to inertia of the piezoelectric element and mass of attached hardware. Thus, the initial waves produced by the piezoelectric ultrasonic transmitter may not be detected by the receiver. If the receiver misses one or more transmitted waves, the time-of-flight measurement will be overstated.
In addition, piezoelectric ultrasonic transmitters are generally very directional such that emissions from the piezoelectric ultrasonic transmitter are stronger along one direction or axis and significantly weak along other directions. Changing an location or orientation of the piezoelectric ultrasonic transmitter can significantly affect the strength of the emission directed towards the receiver. Thus, weaker emissions from the piezoelectric ultrasonic transmitter may not be detected by the receiver if the location or orientation of the piezoelectric ultrasonic transmitter is changed and the time-of-flight measurement will be negatively affected.
Accordingly, a method for accurately and precisely determining a location of an emitter relative to a plurality of receivers would be useful. In particular, a method for accurately and precisely determining a location of an emitter relative to a plurality of receivers that does not rely upon time-of-flight would be useful.